Premovement, sensory, and cognitive brain potentials were
recorded from patients with Chronic Fatigue Syndrome (CFS) in
four tasks: i) target detection, ii) short-term memory, iii)
self-paced movement, and iv) expectancy and reaction time
(CNV). Accuracy and reaction times (RTs) were recorded for
tasks i, ii, and iv. Results from CFS patients were compared
to a group of healthy normals. Reaction times were slower for
CFS patients in target detection and significantly slower in
the short-term memory task compared to normals. In target
detection, the amplitude of a premovement readiness potential
beginning several hundred milliseconds prior to stimulus onset
was reduced in CFS, whereas the poststimulus sensory (N100)
and cognitive brain potentials (P300) did not differ in
amplitude or latency. In the memory task, a negative potential
related to memory load was smaller in CFS than normals. The
potentials to self-paced movements and to expectancy and RT
(CNV) were not different between groups. The findings in CFS
of slowed RTs and reduced premovement-related potentials
suggest that central motor mechanisms accompanying motor
response preparation were impaired in CFS for some tasks. In
contrast, measures of neural processes related to both sensory
encoding (N100) and to stimulus classification (P300) were
normal in CFS.